WO2013181030A1

WO2013181030A1 - Liquid optical adhesive compositions

Info

Publication number: WO2013181030A1
Application number: PCT/US2013/042140
Authority: WO
Inventors: Serkan YURT; Jason D. Clapper; Ross E. BEHLING; Christopher J. Campbell; Mark F. Ellis
Original assignee: 3M Innovative Properties Company
Priority date: 2012-05-29
Filing date: 2013-05-22
Publication date: 2013-12-05
Also published as: CN104520337A; TW201402753A; CN104520337B; KR20150011012A; JP2015526533A; KR101642635B1; TWI577773B; US20150184031A1; JP6333241B2; SG11201407923TA; US9309443B2

Abstract

The disclosure describes a curable composition comprising a) a solute (meth)acryloyl oligomer having a plurality of pendent, ethylenically unsaturated, free-radically polymerizable functional groups and nucleophilic, hydrophilic groups, a) M_w of 5k to 30k, a T_g < 20°C; b) a solvent monomer component; and a photoinitiator. The curable composition may be used as an adhesive in optical applications.

Description

LIQUID OPTICAL ADHESIVE COMPOSITIONS

Field

The present disclosure relates to optically clear adhesives and laminates that include the adhesives,

Optically clear adhesives are finding wide applications in optical displays. Such

applications include bonding polarizers to modules of a liquid crystal display (LCD) and attaching various optical films to a glass fens in, for example, mobile hand held (MHH) devices, During use, the display can be subjected to various environmental conditions, such as high temperature and/or high humidity,

It has been observed that adhesives can exhibit a cloud point, after- subjecting optical laminates of optical films and adhesives to high temperature/humidity accelerated aging tests a¾d subsequently cooling the laminates down to ambient conditions, While still hot, the laminates may be perfectly clear, even when saturated with moisture. But upon cooling they can exhibit a cloud point and turn hazy or "white". Frequently, the haze will disappear over time upon storage of the laminate under amb en conditions. The haze disappearance can often be accelerated by gently heating the optical laminates.

.Saltans ary

The present disclosure includes a curable composition comprising a) a solute

(meth)aeryloy! oligomer having a plurality of pendent, ethyienical!y unsaturated, free-radically polyraerizahle functional groups and pendent hydroxy! groups, a ,M_W of 5k to 30k, a T₈. < 20^i>C {preferably having a. T„ < 0°C); b) a solvent monomer component; and a -phoiomitiatof.

The composition, when cured, is non-yellowing, exhibits low shrinkage, low birefringence ar¾d low sensitivity to moisture (cloud point-resistant), making it. suitable for many optical applications including, but not limited to bonding polarizers to modules of a liquid crystal display (LCD) and attaching various optical films to a glass lens in, for example, mobile hand held

(MHH) devices. The composition is low viscosity so that it may be used as a dispensable optical adhesive, and builds molecular weight by a chain-growth addition process.

in one aspect, an optically clear laminate is provided that includes a first substrate having at least one major surface, a second substrate having a least one major surface, and the cured optics! adhesive composition disposed between the two substrates. The articles of the disclosure may have a thickness greater than about 0,5 millimeters, generally a birefringence (absolute) of less than 1x1 O light transmission greater than about 85%:, preferably greater than 90%, and a CIELAB b* less than about 1.5 units, preferably less than about 1 ,0 unit for samples with thickness of 500 microns.

In a further aspect, an optically clear laminate is provided that includes a firs substrate having at least one major surface, a second substrate havin at least one major surface, and a cloud point-resistant, optically clear adhesive composition situated between and in contact with at least one major surface of the first substrate and at least one major surface of the second substrate, wherein the adhesive has a moisture-vapor transmission rate of at least 400 g m day.

By incorporating hydrophilic moieties in the liquid optical adhesive matrix, haze-free, cloud point-resistant adhesives can be obtained which remain clear even after high

temperature humidity accelerated aging. tests. The provided adhesives are suitable for use in, for example, laminating polarizers to optical LCDs, attaching various optical films to glass lenses in mobile handheld devices, and other adhesive^'- application that require optical clarity in .various temperature and humidity environments.

Although not wishing to -be bound by theory, it is thought that the haze- appears when the adhesive becomes saturated with water at elevated temperatures, and. the concentration of water exceeds the cloud point when quickly .cooled due to poor compatibility of the moisture with th adhesive matrix. This can result in phase separation of small water droplets, which due to a ^•mismatch in refractive index with the adhesive matrix causes haze or a "white" appearance. If the droplets remain very, small (e.g., a few hundred nanometers or less) or the water remains fully solubilized in the adhesive under ambient conditions, the adhesive and its bond line with the substrate will stay clear while it re-equilibrates its moisture content with the- environment. To facilitate . re-equil ibration of the- moisture with its environment, it is also anticipated that the ^•moisture-vapor transmission rate of the adhesive needs to be- high enough to transport the water at a sufficiently high rate to prevent water accumulation which may lead to light scattering nd haze.

As used herein;

"cloud point" refers to the temperature at which a mixture of adhesive and water separate into a continuous adhesive phase and a dispersed water phase, where the dispersed phas Is larger than the wavelength of light and thus make the adhesive appear "white" or cloudy;

"Alky!" means a linear or branched, cyclic or acyclic, saturated monovalent hydrocarbon having from one to about 32, e.g., methyl, ethyl,. 1 -propyl, 2-propyi, pentyl, and the like. "Alkylene" means & linear saturated divalent hydrocarbon having from one to about twelve carbon atoms or a branched saturated divalent hydrocarbon radical having from three to about twelve carbon atoms, e.g., methylene, ethylene, propylene, 2-methylprQpyiene, pentylene, hexylene, and the like.

"Heieroalkyl" includes both straight-chained, branched, and cyclic aikyi groups with one or mor heteroatoms independently selected from S, P, Si, O, and N with both unsubstituted and substituted alky! groups. Unless otherwise indicated, the heteroalkyl groups typically contain from 1 to 20 carbon atoms. "Heteroaikyt" is a subset of "hydrocarbyl containing one or more S, N, O, P, or Si atoms" described below. Examples of "heteroa!kyl" as used herein include, but are not limited to, methoxy, ethoxy, propoxy, 3,6-dioxaheptyI, 3~(irimethylsilyi)-propyl, 4- dimethylarainob iyl, and the like. Unless otherwise noted, heteroalkyl groups may be. mono- or polyvalent, i.e. monovalent heteroalkyl or polyvalent heteroalkylene.

"Aryl" is an aromatic group containing 6-18 ring atoms and can contain optional fused rings, which may be saturated, unsaturated, or aromatic. Examples of an ary! groups include phenyl, naphthyl, btjphenyl, phenantbryL and anthraeyl Heteroaryl is an aryl containing 1-3 .heteroatoms such as nitrogen, oxygen, or sulfur and can contain fused rings. Some e amples of ^•heteroaryl groups are pyridyL furanyl, pyrro!yl, thienyl, thiszolyl, oxagDlyi, inudazoiyJ, Indolyl, benzofuranyl,_. and benzth: iazolyl. Unless otherwise noted, aryl and .heieroaryl groups may be mono- or polyvalent, i.e. monovalent aryl or polyvalent aryiene.

*'(HeteiX))hydrocarbyP^* is inclusive of hydrocarbyl aikyi and aryl groups, and

heterohydroearby! heteroalkyl and heteroaryl groups, the later comprising one or more catenar oxygen .heteroatoms such as ether or amino groups. Heterohydroearby! may optionally contain one or more catenary (In-chain) functional groups including ester, amide, urea, urethane, and carbonate^' functional groups. Unless otherwise indicated, the uon»polymerie ^'(hetero)hydrocarbyi groups typically contain from 1 to 60 carbon atoms. Some examples of such heterohydroearby Is as used herein include, but are not limited to, methoxy, ethoxy, propoxy. 4-diphenylam¾^'obutyl, 2- (2 -phetioxyeihoxy)ethy!, 3,6-dioxaheptyl, 3,6-dioxahexyi-6-phenyl, in addition to those described for "aikyi", "heteroaikyP, "aryl", and "heteroaiyr supra.

"acryloyP is inclusive of both esters and amides.

"(meth)aery!oyi" includes both acryloyl and methacryloyl groups; I.e. is inclusive of both esters and amides. Detailed Descripiioa

Oligomer

As a first component, the adhesive composition has a solute (meik)aeryolyl oligomer having a M_w of 5 to 30k, preferably 8 to 15k, and & T_s of < 20°C, preferably < 1Q°C, more preferably < 0 'C, a solvent diluents monomer component and a phofoinkiator. in some

embodiments the composition comprises:

greater than 50 parts by weight, preferably greater than 80 parts and most preferably greater t n 90 parts of an oligomer having a plurality of pendent free-radically polymerizable functional groups and having a M_¾ of 5 ΐο 30 and a T₈ of < 20°C;

less than 50 parts by weight, preferably less than 20 parts, and most preferably less than 10 parts of a diluent solvent monomer component;

and 0,001 to 5 parts by weight, preferably 0.001 to 1 , most preferably 0,01 to Q. parts of a photomitiator, based on 100 parts by weight of the oligomer and diluent solvent monomer.

The oligomer generally comprises polymerized monomer units of:

a) greater than 50 parts by weight, preferably greater than 75 parts by weight, .most preferably greater than 80 parts by weight of (meth)aeryiate ester monomer imils;

b) 10 to 49 parts by weight, preferably 10 to 35 parts by weight, most preferably 15 to 25 parts by weight, of monomer units having a penden hydroxy functional group,

c) 1 to 10 parts by weight, preferably I to 5 parts by weight most preferably I to 3 parts by weight, of monomer units having a pendent, free-radically polymerizable functional groups,

d) 0 to 20 parts by weight of other polar monomer units, wherein the sum of the

monomer units is_. 100 parts by weight.

In one aspect, the oligomer comprises (meth)acry_a e ester monomer units, (me h)acrylate ester can include aliphatic, cyc!oaliphatic, or aromatic alkyi groups. Useful alky! aerylates (i.e., acrylic acid alky! ester monomers) include linear or branched monofttnctionai acrylates or meihacrylates of non-tertiary alkyi alcohols.

Useful monomers include, for example, 2-ethyihexyI (meth)acry!aie, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyi (meth)acrylate, isopropyi (meth)acryiate, pentyl (raeth)acrylate_s n-ociyl (meth)acrylate, isooctyl (meth)acry3ate, isononyl (methjacryiate, n-butyl (meth)acrylate, isobutyi (meth)aor late, hexyl (meih)acryiate, n-nonyl {meth)acrylate, isoamyl (roeth)acryiate, n- deeyi (roeth)acrylate, isodecy] (raeth)acryiate, lauryl{meih)acrylaie_s dodecyl (meth)acryiate, cyclohexyl (meth)acrylate, phenyl mem(aery1aie), benzyl mefh(acryiate), tridecyl (meth)acr 'Iaie_s 2-propy.heptyl (meth)acryralte and 2-methylbutyl {meth)acrylate, and combinations thereof, in some embodiments, the average carbon number of the alkanol portion of the (rneth)acry!ates is 10 to 14.

The oligomer has a T_g f < 20°C, preferably <10^ftC, mo e preferably <0°C. A useful predictor of biterpolymer T₈ for specific combinations of various monomers can be computed by application of Fox Equation : !/T_g -∑Wi T_gi. In this equation, T_? is the glass transition

temperature of the mixture, Wi is the weight fraction of component i in the mixture, and T_gi is the glass transition temperature of component i, and all glass transition temperatures are in Kelvin ( ). In order that the oligomer have a T_g < 20°C, it is expedient to include low T_g monomers.

As used herein the term 'low T_g monomer" refers to a monomer, which when

hornopolymerized,, produce a (me h)acryloyi copolymer having a Ί of < 20°C. The incorporation of the low T₈ monomer to the oligomer is sufficient to reduce the glass transition temperature of the resulting copolymer to< 2ifC_f as calculated using the Fox Equation. Alternatively, the glass transition temperature can be measured in a variety of known ways, including, e.g., through differential scanning eaiorimetry (DSC).

Suitable- low T_s monomers have one eihylenieally unsaturated group and a glass transition temperature of less than 20 "C, preferably less than 10 °C, (as estimated by the Fox Equation), which are suitable in the present disclosure include, for example, n-bufyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethyl«hexylacrylate_? isoociylacry!ate, eaprofactoneacrylate,

isodecyiacrylate, trideeylacry!ate, laoiylmethaery!aie, meihosy^polyethy!englycol- monomethacrylate,_. laurylacrylate, tefeahydrofarfiiryl-acrylate, ethoxy-eihoxyethyi acrylate and ethoxylated-nonylacryiate. Especially preferred are 2-ethyI~hexylacryIaie, eihoxy-e hoxyethyl acrylate, iridecylacrylate nd ethoxylated nony I acrylate.

In some embodiments the (meth)acsylie acid ester monomer component may comprise (meth)acryla.ie esters of 2-alkyl alksnols wherein the molar carbon number average of said 2-alky! aikanols is 12 to 32. The Guerbet alkanoi-derived (meth)acryhc monomers have the ability to form (co)polymers with unique and improved properties over comparable, commonly used adhesive acrylate (co)polymers. These properties include a very low T,, a low solubility

parameter for acrylic- .polymers, and a. low storage modulus creating a very conformable elastomer. When Guerbet monomer a e included, the (meih)aerylate ester component may include up to 100 parts by weight, preferably up to 50 parts by weight of the {mefh)acrylate ester monomer component. Such Guerbet (meth) cryiate esters are described in Applicant's U.S. 8,137,807 (Lewandowski et ai,) and is incorporated herein by reference.

la some preferred embodiments, the (meth)acry late ester is derived from alkanols having an average carbon . umber of Cg-Cjj, preferably C50-C14. This average carbon number may be calculated based on the weight percentages of each (meth)acrylate ester monomer.

The oligomer further comprises a hydrophilie, hydroxy! functional monomer. The hydrophilie, hydroxy! functional monoraeric compound typicaily has a hydroxy! equivalent weight of less than 400. The hydroxy! equivalent molecular weight is defined as the molecular weight of (he monomelic compound divided by the number of hydroxy! groups in the monomeric compound

The hydroxy! functional monomer has the general formula:

? is a hydrocarb l group, including alky!ene, aryfene and combinations thereof, more preferably

R⁴ is -H or C d alky!;- and

X^! is · ΝΤΓ- or -0-.

Useful monomers of this type include hydroxyeihyl (rneih)acrylate, hydroxypropyl (meth)acrylate, 2-hydroxy-2~phenoxypropyl {meih)acry!ate, and hydroxybutyl (meth)aeryiaie_s 2- hydtoxyethy!acrylamid-e, and -hydroxypropylacryiarrnde.

The hydroxy! functional mon mer is generally used in amounts of 10 to 49 parts by weight based u n 100 parts total monomers of the oligomer.

The oligomer optionally further comprises a hydrophilie polar monomer, other than the hydrox !-functional monomer. The hydrophilie monomer typically has a average molecular weight ( _B) of greater than about 70, or greater than about 500, or even higher. Suitable

hydrophilie polymeric compounds include polyethylene oxide) segments, hydroxy! functionality, or a combination thereof. The combination of polyfeihylene oxide) and hydroxy! functionality in the polymer needs to be high enough So make the resulting polymer hydrophilie. By "hydrophilie" it is meant that the polymeric compound can Incorporate at least 25 weight percent of water without phase separation.

Typically, suitable hydrophilie polymeric compounds may contain po!y(ethylene oxide) segments that include at least 10, at least 20, or even at least 30 ethylene oxide units.

Alternatively, suitable hydrophilie polymeric compounds include at least 25 weight percent of oxygen in the form of ethylene glycol groups from polyethylene oxide) or hydroxy! functionality based on the hydrocarbon content of the polymer.

Useful hydrophiKc polymer compounds may be eopolyraerizable or non-eopo!ymerkable with the adhesive composition, as long as they remain miscib!e with the adhesive and yield an optically clear adhesive composition. Copolymenzabte, hydrophilic polymer compounds include, for example, CD5S2, available from Sartomer Company. Extoa, PA, which is a roOBOfimctional methoxylated polyethylene glycol (550) methacrylate, o SR9036, also available from Sartomer, that is an ethoxylated bisphenol A dimethacrySate that has 30 polymerized ethylene oxide groups between th bisphenol A moiety and each methacrylate group. Other examples include

phenoxypolyethylene .glycol acrylate available from Jarchem Industries lac, Newark, New Jersey,

The polar monomer component may also include weakly polar monomers such as acrylic monomer containing carboxylic acid, amide, urethane. or urea functional groups, in general,, the polar monomer content in the adhesive can include less than about 5 parts by weight or even less than about 3 parts by weight of one: or more polar monomers . Useful carboxylic acids include acrylic acid and mcthacry!ic acid. Useful amides include N-vinyl eaproiactam, N-vinyl pyrrol idone. (meth}acryiamide, N-methyi (meth)acry!amide, Ν,Ν-dimethyl acr lamide, N.N- dimethyl meth(acrykmide), and N-octyl ^'{meth)acrylaiHide.

The hydroxyl functional monomer and polar monomers are used in amounts such that the oligomer is hydrophil c. By "hydrophilic" it Is meant that the o!igomeric compound can incorporate at least 25 weight percent of water without phase separation. Generall ^'the polar monomer are used in amounts of 0 to 20 parts, based on 100 parts total monomer of the oligomer. Generally th polar monomer,, when present is used in amounts of Ho 10 parts, preferabl 1 to 5 parts.

The oligomer optionally contains silane monomers · Mⁱ"^feBS] including those with the following formiiia; wherein;

A is an ethyienscally unsaturated polymerizable group, including vinyl, allyi, vinyioxy, ali loxy, and (meth)acryloyl, preferably (meth)acry!ate;

s is a covalent bond or a divalent (lietero)hydrocarbyi group.

in one embodiment R⁸ is a divalent hydrocarbon bridging group of about 1 to 20 carbon atoms, including aiky!ene and arylene and combinations thereof, optionally including in the backbone 1 to 5 moieties selected from the group consisting of ~0~,, -C(O)-, -S-, -S<¾- and - R¹- groups (and combina tions thereof such as -C(Q)-O-), wherein R^{ is hydrogen, or a C Q alky! group. In another embodiment, R^s is a poly(aiky!ene oxide.) moiety of the formula

the mole ratio of fig is at least 2: 1 (preferably at least 3: 1 ), and R* is H or a C_rC._} aikyi.

Preferably, R⁸ is a divalent aikylene.Y is a hydroiysabie group, including a!koxy, acyloxy and halo; R* is a monovalent alky! or aryi. group, p is L 2 or 3, preferably 3.

Useful silaoe monomers include, for example, 3-(methacryioyIoxy)

propyltrimethoxysiiane, 3 -aeryloxypropyltrimetfeoxysiiane, 3-acryioyloxypropyitriethoxysUane, 3- (methacry1oyloxy)propyiti^,iethoxysiiane_} 3-{methacr oyioxy)propylmetbykiimethoxysiiane_I 3- (acrv oy1oxypropyI)meihyldimethoxysi ane_J 3-(methacrykjyioxy)propykii!nethy.let oxysi!ane. 3- (raethacry!oyloxy) propyldiethyletboxysUane- vmyldimethyiethoxysilane,

v yimethyldiethoxysilane, vmyltriacetoxysi!ane, vinyltriethoxysilane, vinyltriisoprGpoxysiiaae,. vinyltrimethoxysHane. vmyltriphenoxysilane, vinyltri-t-butoxysi!ane, vinyltris-isobutoxysifane, viny!tri-isopropenoxysikne, vinyliTis(2.-methexyeihoxy}si1ane._i and mixtures thereof.

The optional sitae monomers [M^s,i] .are used in amounts of 0 to 10, preferably 1-5, parts by weight, relative to 100 parts by weight -total monomer. Such optional si!ane monomers are used as adhesion promoters for improved bonding to metal, to silaceous surfaces, to surfaces having -OH groups, or as a seif-crosslinking group for the curable composition.

The oligomer further comprises polymerized monomer units having a pendent

ethylenically^' unsaturated polymerizable group. The ethyienicai!y unsaturated group is provided to the oligomer by an indirect route whereby a portio of the pendent hydroxy! groups of the oligomer are further functional ized by reaction with a co-reaciive, eiectrophiiic compound having an ethyieniea!!y unsaturated group - "co-reactive monomers".

The co-reactive- functional group preferably comprises a c-arboxyl, isocyaiiato, epoxy, anhydride, or oxazolinyl group, oxazolinyl compounds such as 2~ethenyf- i ,3-oxazoHfi~5-one and 2-p.ropeny1- ,4-dimethyl-] _;3-oxazoiin-5-one; ©arfjoxy-substjtuted -compounds such as

(meth)acrylic acid and 4-carboxybenzyl (meth)acrylate; isocyanato-substiiuted compounds such as isoeyanatoethyl (meth)aerylaie and 4-isocyanatocycIohexyl (meth)acryiate; epoxy-substiluted compounds such as glycsdyi (meth)acr iate; azirtdmyi-substituted compounds such as N- acryioylaziridine and I-(2-propenyl)-aziridine; and acrylo l halides such as (meth)acryloyl chloride.

Preferred co-reactive monomers have the general formula

wherein R is hydrogen, a C< to C₄ aikyl group, or a phenyl group, preferably hydrogen or a methyl group; IS is a single bond or a (hetero)hydroearb l divalent linking group that joins an ethyl enica!ly unsaturated group to co-reactive functional group A and preferably contains up to 34, preferably up to 18, more preferably up to 10, carbon and, optionally, oxygen and nitrogen atoms and, when ^" is not a single bond, is preferably selected from ff . „ ft .

— R^J— , COW— ' ^and — CNHR

wherein R³ is an alkylene group having I to 6 carbo atoms, a 5- or 6-membered cy oalkylene group having 5 to 10 carbon stores, or an alkylene-oxyalkyiene. in which each alkylene includes ! to 6 carbon atoms or is a divalent aromatic group having 6 to 16 carbon atoms; and A is a co- reactive functional group capable of reacting with pendent hydroxy! group of the oligomer for the incorporation of a free-radically polymerizable functional group.

An alternate but direct m th d of incorporation of the pendent ethy!e caliy unsaturated group is to include a poiyethy!enicaUy unsaturated monomer (s eh as ethylene glycol diaerylate, propylene glycol dimethacrylate, trimethylolpropane triacryfate, or 1,6-- hexamethylenedioidiacrylate)- in the monomer mix. However, it has been determined that, the use of such polyethyfenicaliy unsaturated monomers leads to extensive branching and/or crossltnking, and is therefore precluded in favor of the indirect method of function a? izing a portion of the pendent hydroxy! groups. Preferably, the curable composition contains no po!yethylenically unsaturated monomer or other cross!inkmg agents.

The^' ligomer is -prepared and then subsequently furictiona zed with the pendent, et ylenically unsaturated group. That is. the acrylic ester monomer, hydroxy! functional monomer and optional other polar monomer are comb ned -and polymerized to produce the hydroxy! functional oligomer.

The oligomer may be prepared using radical polymerization techniques by combining an initiator and monomers in the presence of a chain transfer agent, in this reaction, a chain transfer agent transfers the active site on one growing chain to another molecule that can then start a new chain so the degree of polymerization may be controlled. The M_w of the oligomer is 5 to 30 , preferably 8 to 15k. f t has been found if the degree of polymerization Is too high, the composition is too high in viscosity, and not easily proeessible. Conversely, if the degree of polymerization is too low, the modulus, adhesion and other mechanical properties are diminished (at a constant degree of fimctionaiization).

Chain transfer agents ma be used when polymerizing the monomers described herein to control the molecular weigh of the resulting oligomer. Suitable chain transfer agents include halogenatsd hydrocarbons (e,g., carbon tetrabroraide) and sulfur compounds (e.g., lauryl mercaptan,. butyl mercaptan, ethanethiol, and 2-mercaptoethyl ether, isooctyi thioglycolate, t~ dodecylmercaptan, 3-mereap†o~1 2 -propanediol), and ethylenegiyco! bisthlog!yeo!ate. The amount of chain transfer agent that is useful depends upon the desired molecular weight of the oligomer and the type of chain transfer agent.. The chairs transfer agent is typically used in amounts from about 0.1 parts to about 10 parts; preferably 0.1 to about 8 parts; and more preferably from about 0.5 parts to about 4 parts based on total weight of the monomers.

The monomers and optional chain transfer agent are combined and oKgotnerized in the presence of a chain transfer agent. More particularly, the adhesive is prepared by the steps of:

(i) providing an essentially solvent-free mixture comprising the free radically polymerizable monomers supra and at least one free-radical polymers .zatlon initiator,

(ii) partially polymerizing said mixture to provide a partially polymerized mixture exhibiting a Brookfieid viscosity of between 1 ,0110 and 125,000 mPas at 20°C. and a degree of conversion of monomers to polymer of between 85-99 wt %, preferably 90 to 98 wt.% with respect to the mass of the monomers prior to polymerization,

( ii) converting a potion of the hydroxy! functional monomer units to pendent polymerizable

(meth)acrylate groups,

^'(iv) adding one or more photomiiiaiors and solvent diluent monomers to the partially polymerized mixture to provide a radiation-curable precursor,

(iv) subsequently applying the radiation-curable^' precursor to a substrate, and

(v) further polymerizing the radiation-curable precursor by subjecting it to actinic irradiation to provide said adhesive.

The present disclosure further relates to a radiation-curable precursor obtainable by performing steps (i)-(v) of the method of the present disclosure. The polymer obtained by^¬ conversion of the -monomers to polymer to a degree of between 85-99 wt % which is comprised in the radiation-curable precursor, preferably has a polydisperslty p-M¾' _n between. 1.5 and 4.

The mixture further comprises an effective amount of one or more, free-radical

polymerization initiators. The free-radical polymerization initiators and their amount and the polymerization conditions are selected to effect a partial polymerization of the mixture providing the required conversion of monomers to polymer to a degree of between 85-99 wt. % with respect to the mass of the monomers prior to polymerization, and a viscosity of the partially polymerized mixture of between 1,000-500,000 mPas at 20°C. The term "free-radical polymerization initiators" as used above and below includes initiators which can be thermally activated or activated by actinic radiation such as, in particular, UV -radiation. Since the mixture preferably is partially prepolymerized its step (ii) under essentially adiabatic polymerization conditions, the mixture preferably comprises one or more thermally activatable free-radical polymerization initiators. Suitable thermally activatable free-radical polymerization initiators include organic peroxides, organic hydroperoxides, and azo-group initiators which produce free-radicals. Useful organic peroxides include but are not limited to compounds such as benzoyl peroxide, di-t-amy! peroxide, t-butyl peroxy ben oate, and di-cumyl peroxide. Useful organic hydroperoxides include bat are not limited to compounds such as t-amyl hydroperoxide and t-butyl hydroperoxide. Useful azo-group initiators include but are not liinited to the Vazo™ (compounds manufactured by DuPont, such as Vazo™ 52 (2,2'-azobis(2,4- dimethylpentanenitriie)), Vazo"" 64 (2,2'-azobis(2-methyl-propaner.itrile)), \'a 67 (2,2'~ azobis(2-melhylbutanenitrile)>, and Vaz ^SS (2,2'-azobis(^'cyciohexane-carbositrile)).

The polymerization steps (ii) and (in) may occur as a single step, or multiple steps. That is, all or a portion of the monomers and/or the initiator ma be initially charged and partially polymerized. .In some embodiments, there is an initial charge of monomers and initiator that is partially polymerized, then additional .monomer and/or initiator is added, then farmer

polymerized. Such multiple polymerization steps 1) helps narrow the polydispersity of the ^•reaction, specifically reducing the amount of low molecular weight chains formed and 2) minimize the heat of reaction and.3) allows one to adjust the type and amount of monomer available during polymerization.

The term "essentially adiabatic polymerization" as used above md below^, means that total of the absolute value of any energy exchanged to or from the reaction system in which fee polymerization of the mixture to a degree of conversion of between 30-60 wt, % to provide the partially polymerized mixture, takes place, will be less than about 15% of the total energy liberated during said polymerization of the mixture.

in the preferred method of the present disclosure, the reaction system in which the adiabatic polymerization of the mixture to a degree of conversion of monomers to polymer between 85-99 wt.% to provide the partially .cured mixture- takes place, preferably is a batch reactor. By reacting batch- wise is meant that the polymerization reaction of the mixture occurs in a vessel where the partially cured mixture may be drained from the vessel at the end of the polymerization and not continuously during the reaction. The monomers and initiators and, optionally, additives can be charged to the vessel at one time prior to reacting, in steps over time while reacting, or continuously over a time period while reacting, and the polymerization reaction is allowed to proceed for the necessary amount of time to achieve the desired degree of conversions of said one or more monomers to polymer to a degree of between 85-99 wt. %.. The degree of conversion can be measured by standard analytical methods, including 1R spectroscopy and gravimetric analysis. Additional details regarding the adiabatic reaction process may be found in U.S. 7,691,437 (Ellis et ah), incorporated herein by reference.

The oligomer thus produced has the general formula:

~[M^Es¾,]_a M^OH]_b M^Poiai]_s- M^SIY3^_? where

~ M^!;itei]-- represents imerpoiymerized (metb)aerylate ester monomer units;

-[M ^H]- represents interpolymerized (meth)aeryloyl monomer units having a pendent hydroxy group,

F ^Po!arjj represent optional polar monomer units, and

[M^Stiyi] represent optional silane-funetioival monomer units.

Subscripts a, by c and e represent the parts by weight of each monomer unit. It will be understood that the oiigomeric product of the adiabatic process further comprises unreacted monomer due to the partial conversion.

As previously described, a portion of the hydroxy! functional monomer units, -(M⁰*']-, are converted to [M^Aciy!j {meth^aeryloy- monomer units having a pendent po!ymerizable

(meth)aeryIoy1 group to. yield an oligomer of the formula;

H:M^ES¾ M°¾. ^}_C- [M^{Ac: i}],i- M^Syih where

[M^Ae!>!] represents nt&rpolymer&ed (meth)acryioyl monomer ^'units having a pendent

polymerizable (meth)acryIoyl group, b* represents the parts by weight of the ydroxyl-functional monomer remaining after functional! zation to produce [M^Aci>i] and d represents the parts ^'by weigh of the monomer units having pendent., free radically poiymerizabie monomer units, ft will be .apparent that b* + d will equal the value of b in the start ing oligomer. A ^'percent of the pendent hydroxy! groups are functiona!tzed with (meth)acrylate groups to provide the oligomer with 1 to 10 wf.% of (meth)aery!ate groups for subsequent |x !yroertzation. Post-functionalization, it is preferred that the oligomer comprises at least 10 wt¾, preferably at least_. IS wt.% and most preferably at least 20 wt,%, of the hydroxy! functional monomer units so as to avoid the cloud point problems in humid environments.

The extant oiigomeric mixture described supra is combined with a photoinitktor and additional diluent monomer, then further polymerized. The diluents monomers can be used to adjust- he viscosity of the composition. Up to 50, preferably up to 20, more preferably up to 10, parts by weight of diluent monomer may be added.

The diluent monomers may be the same monomers described supra, i the amounts described. In some embodiments the diluent monomer component comprises:

80 to 100 parts by weight of (meth)aeryiaie ester monomers; 0 to 20 parts by weight of hydmxy-fimctional monomers;

0 to 5 parts by weight of polar monomers;

0 to 2 parts by weight of silyl functional monomers, wherein the sum of the monomer is 100 parts by weight. In some embodiments the hydroxy i-functional monomer is used in amounts such the curable composition (oligomer + diluent) has a hydroxy! content greater than 8.3 xl 0^"* moi OB/g.

The curable composition comprises less than SO wt% of the diluent monomers and greater than SO wt.% of the solute oligomer, and a photomi iaior in concentrations ranging from about 0.001 to about 5.0 pbw, preferably from about 0,001 to aboisi 1.0 pbw, and mor preferably from about 0,01. to about 0.5 pbw, per 100 pbw of the monomers.

in the fourth step (iv), one or more photoinitiators are added to the partially polymerized mixture to provide the radiation-curable precursor. The term "photomiiiator" as used above and below comprises free-radical polymerization initiators which can be acti vated by some kind of actinic radiation such as for example, light sources, especially UV-light sources, or e-beam sources. Activation by light sources and, .especially, ^'UV-light sources is preferred. Free-radical radiation polymerization initiators which can be activated by light, are often referred to as free- radical photoinitiators. Radiation-curable precursors which include one or more photoinitiators are .preferred. The free-radical, photoinitiators which a e suitable preferably include both type 1 and type I! photoinitiators.

Type I phetohiitialors. are defined to essentially undergo a unbnolecufer bond cleavage - reaction upon irradiation thereby yielding free^radicals. Suitable type I photoinitiators are selected from a group consisting of benzoin ethers, benzil ke als, ,alpha.-diaikoxyacetophenones, .alpha. -hydroxy alky Iphenones and -acylphosphine oxides. Suitable type I photoinitiators are commercially available, for example, as Esaeure ^{Ϊ Μ} KIP 100 from Lamberti Spa. Gall-arate, ^'Italy, or as Irgacure^{1 M} 651 from Ciba-Geigy, Lautertal, Germany,

Type ΙΪ photoinitiators are defined to essentially undergo a bimolecul&r reaction where the photoinitiators interact in an excited state with a .second compound acting as co-initiator, to generate- free-radicals. Suitable type 11 photoinitiators are selected from a group comprising benzophenones, thioxanthones and titanocenes. Suitable co-initiators are preferabiy selected from a group comprising amine functional monomers, oligomers or polymers whereby amino functional monomers and oligomers are preferred. Both primary, secondary and tertiary-' amines can be used whereby tertiary amines are preferred. Suitable type Π photoinitiators are commercially available, for example, as Esacure™ TZT from Lamberti Spa., Gallarate, Italy, or as 2- or 3- methylbenzophenone from Aldrich Co., Milwaukee, Wis. Suitable amine co-initiators are commercially available, for example, as GE OME ™ 5275 from Rahn AG, Zurich, Switzerland, Photomitiators may be used in the liquid compositions when curing with IJV-radiation. Phoiomitiators for free radical curing include organic peroxides, azo compounds, quinines, mtro compounds, acyl halides, hydrazones, mereapto compounds, pyrylium compounds, imidazoles, chlorotriazines, benzoin, benzoin alky! ethers, ketones,, phenones, and the like. For example, the adhesive compositions may comprise ethyi-2_;4,6 rimeihy! enz0ylphei¾ylphosphinate available as LIJCIRJN™ TPO-L from BASF Corp, or 1 -hydroxycyclohexyi phenyl ketone available as IRGACURE™ 184 from Ciba Specialty Chemicals.

The iotai amount of photomitiators and, optionally, of one or more co-initiators typically is in the range of about 0.001 wt, % to about 5 wt % and preferably in the range of about 0.1 wt % to about 3 wt. % with respect to the mass of the curable composition.

The radiation-curable precursor (oligomer and diluent) has a Brookfieid viscosity of between 1,000 to 500,000 mPas, preferably of between 2,000 and 125,000 mPas, more preferably between 2,000 to 75,000 and especially preferably of between 2,000 and 50,000 mPas at 20°C. if the radiatson -eurahle composition is applied to & substrate by printing ¾ preferably has a

Brookfieid viscosity at 20*C of between 1,000 and 30,000 mPas and more preferably between 2,000 and 25,000 mPas.

The curable composition comprising the oligomer, diluents monomer(s) and photoiniiiator is thoroughly mixed and subsequently applied to a substrate in the fifth step (v). Because of its low viscosity the composition can be applied to a substrate by conventional coating methods such as knife-coating, gravure coating, certain coating, air ^'.knife coating and roll-coating. In some embodiments the curable composition is applied by dispensing a fixed amount of adhesive over the- bonding area. This may be applied^' by applying dots and/or lines via a needle, needle die or slo die. The entire area may be coated by spray coating, die coating, draw bar coating or curtain coating, A "dam and fill" method may be used, pree rmg a dam of liquid optically clear adhesive around the perimeter of the bonding, area -and then, filling the bonding area using any of the - methods described, above. The dam may also be in the form of a tape, or a foam and/or rubbe gasket. The area may be coated usi ng stenc il printi ng or screen printing without the aid of a dam. Additional information regarding these deposition methods may be found in WO 2011/1 19828» WO 2011 /84405, U.S. 2010/0265444 and U.S. 2009/0283.21 i (Busman et. a!.), incorporated herein by reference.

Subsequent to its application to a substrate the precursor is further polymerized in step (v) by subjecting it to actinic irradiation and preferably to UV-irradiaiion. Actinic radiation from any source and of any type can be used for the curing of the composition whereby light sources are preferred over e-beam sources. The light can be- in the form of parallel rays or divergent beams. Since many photo initiators generating free-radicals exhibit their absorption maximum in the ultraviolet (UV) range, the light source is preferably selected to m t an effective amount of such radiation. Suitable light sources include carbon arc lamps, mercury vapor lamps, fluorescent lamps comprising ultraviolet light-emitting phosphors, ultraviolet light-emitting diodes, argon glow lamps and photographic flood lamps. Preferred are high-intensity light sources having a lamp power density of at least 80 mW/cm² and more preferably of at least 120 mW cnv\

When subjecting the curable composition to actinic irradiation and, in particular, to UV~ irradiation, the precursor is cured via a free-radical polymerization mechanism. The composition is termed as "fully cured" when the conversion of the oligomer and diluents monomers to polymer is at least 90%, more preferably at least 95%, especially preferably at least 97.5% and most preferably at least 99%.

The energy density applied preferably is 100-5.000 mJ/em² and more preferably 300-3000 mJ/cm² for curing a 2S0 μηι thick layer of the radiation-curable composition.

The curable composition and the photoitfitiator may be irradiated with activating UV radiation to polymerise the monomer components). UV light sources can he of two types; 1} relatively low light Intensity sources such as Blacklights which provide generally 10 mW/enr or less (as measured in accordance with procedures approved by the United States National institute of Standards and Technology as, for example, with a UV!MAP UM 365 L-S radiometer

manufactured by Electronic Instrumentation & Technology, Inc., in Sterling, VA) over a wavelength range of 280 to 400 nanometers; and 2) relatively high light intensity sources such as medium pressure mercury lamps which provide intensities generally greater than 10 mW crrT, preferably 15 to 450 W crn².

Further components and additives may be included ^'into the curable composition such as, for example, heat stabilizers, antioxidants, antistatic agents, thickeners, fillers, .pigments, dyes;, colorants, thixorropie agents, processing aides, nanoparticles, fibers and any combination thereof in amounts such that the optical properties of the adhesive are not significantly compromised. Such additives are generally in an amount of between 0.01 and 10 wt. % and m re preferably in -an amount of between 0.05 and 5 wt. % with respect to the mass of curable composition. In some embodiment the curable composition and subsequent adhesive contai no such additives.

In some embodiments the curable composition may further comprise metal oxide particles to modify the refractive Index of the adhesive layer or the viscosity of the liquid adhesive. Metal oxide particles that are substantially transparent may be used. Metal oxide particles may be used In an amount needed to produce the desired effect, for example, in an amount from about 1 to about 10 weight percent, from about 3.5 to about 7 weight percent, from about .10 to about 85 weight percent, or from about 40 to about 85 weight percent, based on the total weight of the curable composition. Metal oxide particles may only be added to the extent that they do not add undesirable color, haze or transmission characteristics. Generally, the particles can have an average particle size of from about 1 am to about 100 nm.

The metal oxide particles can be surface treated to improve dispersihi!ity in the adhesive layer and the composition from which the layer is coated. Examples of surface treatment chemistries include silanes, siloxanes, carboxylic acids, phosphonic acids, zirconates, titanates, and the like. Techniques for applying such surface treatment chemistries are known.

In some embodiments, the adhesive layer comprises a fumed silica. Suitable fumed silicas include, but are not limited to: AEROS1L™ 200; AEROSIL™ R805; and EVONIK™ VP NKC 130 (both available from Evonik industries); CAB-O-SIL™ TS 610; and CAB-O-SIL™ T 5720 (both available from Cabot Corp.), and !-ID ™ H20RH (available from Wacker Chemie AG). In some embodiments, the adhesive layer comprises a fumed aluminum oxide, such as

AEROXIDE™ ALU 130 (available from Evonik, Parsippany, NJ). In some embodiments, the •adhesive layer comprises cla such as-GARAMlTE™ 1958 (available from Southern Clay Products).

In some embodiments,, the liquid optically clear adhesive comprises non-reactive oligomeric theology modifiers. While not wishing to be bound by theory, non-reactive oiigomersc theology modifiers build viscosity, at low shear rates through hydrogen bonding or other self- associating_, mechanisms. Examples of suitable non-reactive oligomeric fheology modifiers include, but are not limited to: pofyhydroxycarboxyKc acid amides (such as BYK 405, -available from Byk-Chemie GmbH, Wesel. Germany), polyhydroxyearboxyiic acid esters (such as BYK R- 606™, available from Byk-Chemie GmbH, Wesel, Germany), modified ureas (such as

DISPARLON 6100™, DISPARLON 6200™ or DISPARLON .6500™ from King Industries, Norwalk, CT or BY 410™ from Byk-Chemie GmbH, Wesel Ge.mia.ny), metal sulfonates (such ^•as K-STAY ^m 501 from King^' Industries, Norwalk, CT or IRCOGEL 903™ from Lubrizol Advanced Materials, Cleveland, OH), acryiated oligoamines (such as GENOMER 5275™ from Ra n USA Corp, Aurora, IL), polyacryUc acids (such as CARBOPOL 1620™ from Lub izol Advanced Materials, Cleveland, OH), modified urethanes (such as K-STAY 740™ from King Industries, Norwalk, CT), micronized amide waxes (such as CRAYVALLAC SLT™ from Arkema), micronized amide modified castor oil waxes (such as CRAYVALLAC M.T ^!M from Arkema), micronized castor oil derived waxes (such as CRAYVALLAC AN'OSETTLB CVP™ from Arkema), pre-activaied amide wax dispersed in (meth)acrylate monomers (such as

CRAYVALLAC E00054) or polyamides. in some embodiments, non-reactive oligomeric rheo!ogy modifiers are chosen to be miseihle and compatible with the optically clear adhesive to limit phase separation and minimize haze.

In some embodiments, the adhesive layer may be formed from a thixotropic liquid optically clear adhesive. As used herein, a composition is considered thixotropic if the composition shear thins, i.e., viscosity decreases when the composition is subjected to a shearing stress over a given period of time with subsequent recovery or partial recovery of viscosity when the shearing stress is decreased or removed. Such adhesives exhibit little or no flow under zero or near-zero stress conditions. The advantage of the thixotropic property is that the adhesive can be dispensed easily by such processes as needle dispensing due to the rapid decrease in viscosity under low shear rate conditions. The main advantage of thixotropic behavior over simply high viscosity is that high viscosity adhesive is difficult to dispense and to flow during application. Adhesive compositions can be made thixotropic by adding -particles to the compositions, in some embodiments, fumed silica is- added to impart thixotropic properties to a liquid adhesive, in an amount of from about 2 to about 1 Wt.%, or from about 3:.5 to about 7 wt.%.

In some embodiments, the curable composition optionally comprises a thixotropic agent. As .used herein, a composition is considered thixotropic if the composition shear thins, i.e., viscosity decreases when the composition is subjected to a shearing stress over a given period of time with subsequent recovery or partial recovery of viscosity when the shearing stress is decreased or removed. Such adhesives exhibit little or no flow under zero or near-zero stress conditions. The advantage of the thixotropic property -is that the adhesive, can be dispensed easily by such processes as needle dispensing due to the rapid decrease in viscosity under low shear rate conditions. The main advantage of thixotropic behavior over simply high viscosity is that high viscosity adhesive is difficult to dispense and to flow during application. Adhesive compositions can be made thixotropic by add ng particles to the compositions. In some embodiments, fumed silica is added to impart thixotropic properties -to a liquid adhesive, in an amount of from about 2 to about: 10 weight percent, or from about 3.5 to about .7 weight percent The efficiency of the thixotropic agent and the optical properties depend on the composition of the liquid optically clear adhesi ve and its interaction with the thixotropic agent. For example, in the case of associative thixotropes or hydrophilic silica, the presence of highly polar monomers such as acrylic acid, monomers or oligomers may disrupt the thixotropic or optical performance. Consequently, it is preferred that the curable composition contain no acid-functional monomers or oligomers,

in some embodiments, any liquid optically clear adhesive having a viscosity of no more than 30 Pa.s, between about 2 and about 30 Pa^*s and particularly between about 5 and about 20 Pa s at a shear rate of 1 to 10 sec^"' can be combined with a thixotropic agent to form a thixotropic liquid optically clear adhesive suitable for stencil printing or screen printing. The efficiency of the thixotropic agent and the optical properties depend cm the composition of the liquid optically clear adhesive and its interaction with the thixotropic agent. For example, in the case of associative thixotropes or hydrophiiic silica, the presence of highly polar monomers such as acrylic acid, acid or hyxdroxy! containing monomers or oligomers may disrupt the thixotropic or optical perform a¾e ,

The curable composition optionally comprises a plasticizer that increases its softness and flexibility to the resultant. adhesive. Plasticizers are well known and typically do not participate in polymerization of (meth)acry iaie groups. The plastic izer may comprise more than one plasticisser material. The adhesive may comprise from greater than 1 to about 20 weight percent, or from greater than 3 to about 15 weight percent, of the piasticijter. Th particular plasticizer used, as well as the amount used, may depend on a variety of factors.

The curable composition may comprise a taekifier. Tackifiers are well known and are used to increase the tack or other properties of an adhesive. There are many different types of tackifiers but nearly any taekifier can be classified as: a rosin resin derived from wood rosin,, gum .rosin or tali oil rosin; a hydrocarbon resin made from petroleum-based feedstock; or a terpen© resin deri ved from terpens feedstocks of wood or certain fruits. The^' adhesive layer may comprise, e.g., from 0.01 to about 20 weight percent, from 0.01 to about 15 weight percent or from 0, 1 to about 10 weight percent of taekifier. The adhesive layer may be free of taekifier.

The adhesive resulting from photopolyroerixation of the ^'curable composition is desirably •optically clear. As used herein, the term "opticaHy clear" refers to a material thai has a luminous transmission of greater than about 90 percent,, a haze of less than about 2 percent, and opacity of jess than about 1 percent in t e 350 to 800 nra wavelength range. Both the luminous transmission and^' the haze can be determined using*, for example,_. ASTM-D i 003-95, Typically, the optically clear adhesive may be visually free of bubbles .

The adhesive layer desirably maintains optical clarity, bond strength, and resistance to delanlination over the lifetime of the article in which it is used. Whether an adhesive will likely have these desirable characteristics can be determined using an accelerated aging test. The adhesive layer can be positioned between two substrates for this test The resulting laminate is then exposed to elevated temperatures, optionally, combined with elevated humidity conditions, for a period of time. For example, the adhesive layer can often retain its optical clarity after aging at 8S°C for approximately 500 hours without humidity control (i.e., the relative humidity in the oven is usually below about 10 percent or below about 20 percent). Alternatively, the adhesive can often retain its optica! clarity after aging at 65°C for approximately 72 hours with a relative humidity of about 90 percent. Most importantly, the cloud point resistant adhesive can often retain its optical clarity after aging at 6^"5°C for approximately 72 hours with a relative humidity of about 90 percent and rapid (i.e. within minutes) cooling to ambient conditions. After aging, the average transmission of the adhesive between 350 nanometers (ran) and 800 mi cm be greater than about 85 percent and the haze can be less than abou 2 percent.

The adhesive resulting from photopolymerization of the curable composition desirably has a shear modulus of 5000 to 1 ,000,000, preferably 5000 to 100,000, more preferably 5000 to 50,000 pascals.

Laminates are provided that include an optical film or optically clear substrate and a optically clear adhesive layer adjacent to at least one major surface of the optical film or substrate. The articles can farther include another substrate (e.g.. permanently or temporarily attached to the adhesive layer), another adhesive layer, or a combination thereof. As used herein, the term "adjacent" can be used to refer to two layers that are in direct contact or that are separated by one or more this layers, such as primer or hard coating. Often, adjacent layers are in direct contact. Additionally, laminates are- provided that include an adhesive layer positioned between two substrates, wherein at least one of the substrates is an optical film. Optical films intentionally enhance, manipulate, control, maintain, transmit, reflect, refract, absorb, retard, or otherwise alter light that impinges upon a surface of the film. Films included in the laminates include classes of material that have optical functions, such as polarizers, interference polarizers, reflective polarizers, diffusers, colored optical films, mirrors, kaivered optical film, light control films, transparent sheets, brightness enhancement film, anti-glare, and anti-reflective films, and the like. Films for the provided laminates can also include retarder plates such as quarter-wave and half- wave phase retardation optical elements. Other optically clear films include anti-splinter, films and electromagnetic interference filters.

In some embodiments, the resulting laminates can he optical elements or can be- used to prepare optical elements. As used herein, the term "optical element" refers to an article that has an optical effect or optical application. The optical elements can be used, for example, in electronic displays, architectural applications, transportation applications, projection applications, photonics applications, and graphic applications. Suitable optical elements include, but are not limited to, glazing (e.g., windows and windshields), screens or displays, cathode ray tubes, and reflectors.

Exemplary optically clear substrates- include, but are not limited to a display panel, such as liquid crystal display, an OLED display, touch panel, electrowetting display or a cathode ray tube, a window or glazing, an optical component such as a reflector, polarizer, diffraction grating, mirror, or cover lens, another film such as a decorative film or another optical film.

Representative examples of optically clear substrates include glass and polymeric substrates including those that contain polycarbonates, polyesters (e.g., polyethylene

terepbthalates and polyethylene naphthaktes), polvurethanes, poly(meth)a.cryiates (e.g.,

polyraeiriyl methacrylates), polyvinyl alcohols, polyolefins such as poryethytenes, polypropylenes, and cellulose triaeetaies. Typically, cover lenses can be made of glass, polymethyl methacryiates, or polycarbonate.

The laminates have at least one of the following properties: the adhesive layer has optical transmissivity over a asefal .lifetime of the article, the adhesive can maintain a sufficient bond strength between layers of the article, the adhesive can resist: or avoid deiaminaiion. and the adhesive can resist bubbling of the adhesive layer over a usefiil lifetime. The resistance to bubble formation and retention of optical transmissiviiy can be evaluated using accelerated aging tests.

The adhesive compositions of the present disclosure may be applied directly to one or both sides of an optical element such as a polarizer. The polarizer may include additional layers such as an anti-glare layer, a protective layer, a reflective layer, a phase retardation layer, a wide- angle compensation layer, and a brightness enhancing layer. In some embodiments, the adhesives of the present disclosure, may be applied to one or both sides of a liquid crystal cell, it may also be used to adhere a polarizer to a liquid crystal cell. Yet another exemplary set of optical

laminates, include the application of a cover lens to a LCD panel, the application of a touch panel to an LCD panel, the application of a cover lens to a touch panel, or combinations thereof.

Examples

Materials

Abbreviation or Trade Name Description

Isooetyl acryiate, available under the trade designation

IOA

"SR440" from Sartomer USA, LLC, Exton, Pennsylvania,

2-ethylhexyi acryiate, available irom Sigma-Afdrteh Co.

2-EHA

LLC, St. Louis, Missouri.

2-propylheptyl aeryfate, avail le under the trade designation

2-PHA

"2-PHA" from BASF Corporation, Florhara Park, New Jersey.

Tridecy! Aerylate, available under the trade designation

TDA

"SR489D" from Sartomer li S A .

2-faexy3deeyl acry lats, available under the trade designation

C 16 "HEDA 56" from Toho Chemical Industry Co. Ltd,

Kanagawa, Japan.

Lauryl Acrylate, available under the trade designation

LA

"SR335" from Sartomer USA.

isoborayl Acryiate, avai!abie under the trade designation

!BOA

-SR506D" from Sartomer USA.

Oetadecyl acryiate, available from Sigma-AIdrich Co. LLC,

ODA

St. Lo is, Missouri,

h dro butyl acrylate, available under the trade designation

4-HBA

"4-H8A- irom San Esters Corporation, New York, New York.

2 -hydroxy-propyl methaery!ate. available from Alfa Aesar,

2-HPMA

Heysham England.

!soeyanatoet yl methaerylate, available from Showa Denko,

IEM

anagawa, Japan.

Ethylene glyeol bisthioglycolate, available from Evans

EGBTG

Che mi tics LP, Teaneek, New Jersey.

Polypropylene glycol monoacr late, available under the trade

PPA6 designation ^WB isomer PPA6* from" from Cogms, Ciaeina tL

Ohio.

2-ethoxyethoxyeth I acrylate, available from Polysciences,

2EEEA

foe, Warrington, Pennsylvania.

2,2ⁱ-A2.obis 2,4-di5i!etlvyipentanersiiTile)_! available under the

VAZO 52 trade designation "VAZO 52" from E. I. du Pont de Nemours and Co., Wilmington, Delaware.

1 '-Azebis{«graoocyel0hem»e), available under the trade

V ZO S8 designation "VAZO 88" from E, I. d Pont de Nemoars and

Co.

2_J5-Din5ethyi-2_J5-di-(ieit-butylperoxy)hexyne-3_J available

LI 3 under the trade designation "Luperso! 130" from Perm a!i

Corporation, Buffalo, New York.

2,5-bis(teri-bu{yiperoxy)-2,5 -di.Tnethyihex&iie available under

L!O i the trade designation "Luperso! 101 " from Pennwait

Corporation.

EthyL2,4,6^:-trimethy3be:nzoylphe?iy phosphinate, available

TPO-L under the trade designation "Lucirrn TPO-L" from BASF

Cor oration, Florham Park, New Jersey.

A 174 3»methacyrioxypropyltrhnethoxysiiane, .available under the trade designation "Silquest A- 174" from Momentive,

Columbus, Ohio.

2HD 2-hexyH-decanoi, available from Sigma-Aldrich Co. LLC.

TEA Triethylarnme, available from Alpha Aesar,

AC Aeryloyl chloride, available from Alpha Aesar.

Pentaerythritol tetrakis(3 -{ 3,5-di-tert-butyl-4^«

hydroxypheny propionate), a phenolic primary antioxidant

1 G i O!O

available under the trade designation "IRGANOX 1010" from Ciba Specialty Chemicals, fee, Basel, Switzerland,

Octadecyi-3-(3_i5"di-tsrt.butyi-4-hydrox> hesiyl)-prapior¾ai.e_; a phenolic primary antioxidant available under the trade

!RG 1076

designation "IRGANOX 1076" from Ciba Specialty

Chemicals, Inc.

Hytiroquiaone monomethyi ether, available from Alfa Aesar,

MEHQ

Heysham England,

A hydrophobically treated fumed silica, surface treatment of hexadecy!siiane, available under the trade designation

VP NKC 130

"AEROSIL VP N C 130" from Evonik Industries,

Parsippaay, New Jersey,

Poiyi^'eihylene glycol) methyl ether aeryiate, available from

MPEG

Sigma-AWricfe Co, LLC.

TEST METHODS

Viscosity measurements were- made by using an AR2000 Rheometer equipped with a 40 mm, .1° -stainless steel cone .and a plate available from TA Instruments:, New Castle* Delaware. Viscosities were measured at 25^CC using a steady state flow procedure with a frequency from 0.001 to 100 sec" with a 28 urn. gap between the cone and the plate. Viscosity values are reported in centipoise (cps) at a shear rate of I sec^"' ,

M&!es«¾r Ψ^'Φ ί Deteqnjnption

The molecular weight distribution of the compounds was characterized usin conventional gel permeation chromatography (GPC). The GPC msiramentation, which was obtained from Waters Corporation, Milford, MA, included a high pressure liquid chromatography pump (Model 15 15HPLC), an auto-sampler (Model 71 7), a UV detector (Model 2487), and a refractive inde detector (Mode! 2410). The chromatograph was equipped with two 5 micron PL-gel MLXED-0 columns available from Varian inc. Palo Alto, California,

Samples of polymeric solutions were prepared by dissolving polymer or dried polymer samples in tefrahydrofuran at a concentration of 0.5 percent (weight/volume) and filtering through a 0.2 micron po!ytetrafluoroethyiene ft her that is available from VWR International, West Chester, Pennsylvania. The resulting samples were injected into the GPC and elated at a rate of 1 milliliter per minute through the columns maintained at 35°C. The system was calibrated with polystyrene standards using a linear least squares fn analysis to establish a calibration curve. The weight average molecular weight (M ) and the polydlspersity index (weight average molecular weight divided by number average molecular weight) were calculated for each sample against this standard calibration carve.

Eysk Ad esion

Two float glass slides, 2 1/4 inch (5.72 cm) _x \ 3/16 inch (4.60 em) x 1/4 inch (0.635 cm) were cleaned with isopropyl alcohol (IPA). Two layers of SCOTCH Filament Tape 898, available from the 3M Company, Si. Paul, Minnesota, were attached along the two, ί 3/16 inch (4,60 cm) length edges of the first substrate in order to control the thickness of the adhesive composition, once t was placed on the slide. The tape created a step height of about 340 microns. The adhesive composition was dispensed by a pipette in the center of the slide and the second slide was slowly brought into contact with the first slide. The adhesive composition between the slides was cured with the total energy of 3,000 mJ/cm² in UV-A or UV~B region under a Fusion UV lamp available from Fusion UV Systems Inc.. Gaithersbarg, Maryland, using a quartz UV D-buib (Examples 9 through 1 and 26 through 31). The remaining samples (Examples I through 8 and 20 through 25) were cored under an Omnicure 2000 high pressure Hg spot cure source- available- from EXPO Photonic Solutions, Inc., Mississauga, Ontario, Canada, with the total energy of 3,000 mi/err in UV-A region. Samples then dwelled for one day in a controled temperature-humidity (CT!i) room at a temperature -of 74°F (23.3°C) and a relative humidity of 50 % prior to testing.

A glass slide with cured adhesive was loaded into a sliding pluck fixture on an MTS INSIGHT Electromechanical Test Syste with a 5 kN load ceil available from MTS Systems Corporation, Eden Prairie, Minnesota. The samples were pulled apart at 25 mm/mm and tested to failure. The first measured peak load was then divided by the measured area of the adhesive composition on the pluck sample to determine the pluck adhesion, measured in N/cm\ At least- three samples were tested for each adhesive composition, with an average value for pluck adhesion reported.

Sjhnnkage

Percent volume shrinkage was measured using an Accupyc II 1340 Pycnomeier from

Micromeritics instrument Corporation, Norcross, Georgia. An uncured adhesive composition sample of known mass was placed in the silver vial of the pycnometer. The vial was placed in the pycnometer and the volume of t sample as measured and the density of the adhesive

composition- was determined based on the volume and mass of the sample. The density of a cured adhesive composition was measured following the same procedure as thai of the uncured. Cured adhesive compositions were prepared by casting a hand spread c oating of the adhesive composition between two release liners, using an 1 1 mil (0.28 mm) thickness adjuster, and curing with, the total energy of 4,000 mi/cm"⁵ in UV-A region under a Fusion UV lamp with a quartz UV

D bulb available from Fusion UV Systems Inc.

Volume shrinkage was then calculated from the following equation:

{ {!/ Avg Liquid Density) - (1/ Avg Cured Density)] / (1/ Avg Liquid Density )} x 100%

Optical Measurements

Optical properties of the adhesive compositions were measured by sand wiching the adhesive composition between two^' 2 inch (5.08 cm) x 3 inch (7.62 cm) x 200 microns LCD glass panels, EACLE 2000 available from Specialty Glass Products. Willow Grove, Pennsylvania. The adhesive composition was cured with a total energy of 3,000 ml/cm² in UV-A region using a Fusion UV lamp with a quartz UV D bulh, available from Fusion UV Systems Inc. The thickness of the adhesive composition was controlled by applying two layers of SCOTCH Filament Tape 898, 3M Company, along the two. 2 inch (S.08 cm) edges of one of the panels. Haze,_, transmission and color of the cured LOCAs were measured before and after aging under environmental testing conditions using a HimterLab UltraScan PRO available from Hunter Associates Laboratory, fee, Reston, Virginia.

Preparation of Solute (Meth crvoM OHgomers (S AOs

Preparation of .SMAQ-

This example illustrates the process to produce a solute (meth>acryolyl oligomer. Two essentially adiabatic reaction cycles are used with option of a third fu&ctioaa!&sation step, after initial polymer synthesis. To a 5L stainless steel .reaction vessel was added: 1,880 g TDA, 500 g 4- HBA, 40.0 g EG8TG, 2.5 g IRQ 1010, and 20.5 g of 2.44 wt% MEHQ in IOA. The mixture was healed to 60°C and mechanically stirred until all components were dissolved, at which time 60.1 g of 0.125 wt% solids VAZO 52 in IOA was added to the reactor. Once the polymerization had begun the temperature control system was set to cause the temperature of the jacket to track i .5°C above the batch temperature to facilitate adiabatic reaction conditions. At 120°C the jacket stopped tracking the polymerization temperature, which peaked at 132°C and was allowed to coo! back to 60°C before being depressuri¾ed. A sample was taken of the reaction mixture and the unreacted monomer was 27.73% based on the total weight of the mixture.

The following components were charged to a 4oz glass jar: 1.0 g V AZO 52, 0.45 g VAZO 88, 0.45 g L iOI, and 48.10g ethyl acetate. The solution was shaken in a reciprocating mixer until ail solids were dissolved, at which point, 25.0 g of the ethyl acetate solution and ! 3.33g EGBTG were added to the stainless steel reaction vessel and stirred at 60°C. The reaction peaked at I \ ()^aC at which time 50 g of ΪΕΜ was added. The reactor was cooled to IWC and held isothermally for 4 hours and then drained, producing SMAO- 1. The SMAO was stored in 32 oz brown jars. A sample was takes of the reaction mixture and the unreached monomer was 4.38%, based on the total weight of the mixture.

Preparation, of S A.O-2 through SMAC 7

132.5 g of LA, 220 g of 4-HBA, 192.5 g IBOA and 6.6 g of EGBTG were added to a four neck flask equipped with a reflux condenser, thermocouple, mechanical stirrer, nd a gas inlet that allows nitrogen or air to be bubbled into the solution. The first, charge of thermal initiators, VAZO-52 (0.024.8 g), VAZO 88 (0.0248 g) and L130 (0.0248 g) were also added to the flask. The mixture was stirred and heated to 60°C under nitrogen. The temperature of the reaction m ixture quickly exothermed and peaked at around !60^c C, during the polymerization. After the reaction peak, a second charge of VAZO™ 88 (0.0248 g) dissolved in an additional 5 g of LA was added to the flask. The reaction vessel was held at 160^E'G for 90 minutes before cooling to I 00°C and purging with air,

1 1 g of iEM was then added to the batch to react with the pendant hydroxy! groups on the LA''4-BSA/IBOA/EGBTG oligomer chains, incorporating ethaer late functional groups to the oligomer. The reactor vessel was held at ! 00°C for 4 hours and then cooled and drained, producing SMA.O-2. A sample was taken, at the end of this reaction period, for oligomer molecular weight determination by QPC, Tabic 2,

A similar procedure was used to produce SMAG--3 through SMAO- 17. The monomers and amounts used to prepare these additional oligomers are shown in Tables 1 through 3 below, as well as, molecular weight data. Note that VAZO™ 88 is added in two steps, the amount of VAZO in each step being half that indicated in Tables I through 3. Also, during the second charge of VAZO 88, the VAZO 88 was dissolved in 5 g of acrykte, the major aerylaie ester component of die composition. This 5 g of scrylate is included in the values reported in the Tables 1 through 3, Table ! . Formulations of SMAO-2 ihroa h SMAO-8.

Table 2, Formulations of SMAO-9 through SMAO-11.

Preparation of SMAO-18

To a 5L stainless steel reaction vessel was added 2,779 g T A, 665 g 4-HBA, 57,8 g EGBTG, and 28.7 g of 2.44 wt% MEHQ in TDA. The mixture, was heated to 60*C and

mechanically stirred until all components were dissolved, at which time 28.1 g of 0,5 wt% solids VAZO 52 i TDA was added to the reactor. Once the polymerization had begun the temperature control system as set to cause the- temperature of the jacket to track 1 ,5°€ above the batch temperature- to facilitate adiabatic reaction conditions. At 120°C the jacket stopped tracking the polymerization temperature, which peaked at. 134^r and was allowed to cool back to 6Q*C before being depressurized. A sample was taken of the reaction mixture and -the unreacted monomer was 43.68% based on the total weight of the mixture.

The following -components were charged to a 4e¾ glass j ar: 1 ,0 g VAZO 52, 0,45 g VAZO 88, 0.45 g LI 01 , and 48.10 g ethyl acetate. The solution was shaken in a reciprocating mixer until all solids were dissolved, at which point 35,0 g of the ethyl acetate .solution and 19.25 g EGSTG were added to the stainless steel reaction vessel and stirred at 6G°C. The reaction peaked at

110°C. The reactor was then cooled to lOO^C while it was purged with 90/1 nitrogen/oxygen control as for 30 minutes, at which time 70.0g of IEM were added to the reactor and held at 10Q°C isothermaily for 2 hours. After 2 hours ! kg of material was drained from the reaction vessel into brown tinted jars. A sample was taken of the reaction mixture from this step nd the anreacted monomer was 5.07% based on the total weight of the mixture,

Preparation, .of .Adhesive Compositions Examples 1 through 3 1

Adhesive compositions were prepared by charging the component materials, disclosed in Tables 4 through 7, into a white mixing -container available from FlackTek Inc., Landrum, South Carolina, and mixed using a Ha schi id SPEEDMIXER DAC 150 FVZ available from FlackTek Inc. operating at 3540 rpm for 6 minutes, The exceptions to this were Examples 26 through 31 , which were mixed with Hauschiid SPEEDMIXER DAC 600 FV available from FlackTek Inc. operating at 2200 rpm for 4 minutes. Material properties; shrinkage, viscosity and pluck adhesion and optical properties before and after aging under environmental conditions; are described En Tables 8 through 17,

Table 4, Adhesive Compositions of Examples 1-9 (values are in grams).

Table 5. Adhesive Compositions of Examples 10-19 (values are in grams).

Table 6. Adhesive Compositions of Examples 20 to 25 (values are in grams).

Tabie 7. Adhesive Compositions of Examples 26-31 (values are in grams).

Table 8. Optical Properties, Shrinkage, Viscosity and Pluck Adhesion of Exampl

Table 9. Opi icai Properties, Shrinkage, Viscosity and Pluck Adhesion of Examples

Table 10. Optical Properties, Shrinkage, Viscosity and Pluck Adhesion of Examples 7-9.

Table 1 1. Opticai Properties, Shrinkage, Viscosity and Pluck Adhesion of Examples 10-12,

Table 12. Optical Properties, Shrinkage, Viscosity and Piisck Adhesion of Examples 13 5»

Table 13. Optica) Properties, Shrinkage, Viscosity and Pluck Adhesion of Examples 16-19.

Table 14. Optical Properties, Shrinkage, Viscosity and Pluck Adhesion of Examples 20-22.

Visually Hazy

Table 15. Optical Properties, Shrinkage, Viscosiiy and Pluck Adhesion of Examples 23-25.

** Visually Hazy

Table 16. Optical properties, Shrinkage, Viscosity and Pluck Adhesion of Examples 26-28.

Table I S. Optica! properties of Examples 32-34.

Preparation of a Thixotropie Adhesive Composition: Exam e 35

To the 5 L stainless steel reactor containing SMA0 8 described above (less the I kg sample removed for testing), 275 g T DA m nomer, 50 g HBA monomer, 25 g TPO-L

phoioitiittator, 25 g IRG 1076, and 12.5 g AI ?4 were added to the reaction vessel and mixed for 45 minutes, producing at) adhesive composition. 100 g of this adhesive composition was placed in a white mixing container, (a Max 100 cup, from FSackTek inc., Landrum, South Carolina) and 4 g of VP C 130 were added. The components were mixed using a Hausehild SPEEDM!XE DAC 600 FY. from Fiaek ek inc., operating at 2200 rpm for 4 minutes, producing Example 32. The viscosiiy ai different shear rates and optical properties are shown in Table . The viscosity of the adhesive composition was 834 cps at a shear rate 1 see^"'., without the addition of a thsxoirope.

Table 1 . Viscosity and Optical Properties of Example 32.

This disclosure provides the following embodiments: A curable composition comprising: a) a solute (raeth)acryo!yl oligomer having a M_w of 5 to 30k and a T_g of < 20°C comprising

L greater than 50 parts by weight of (meth)acryiate ester monomer units, ii, 10 to 9 parts by weight of hydroxyMunci ona!. monomer units. iii. 1 to 10 parts by weight of monomer units having pendent acryiate grou ,

IV. 0 to 20 parts by weight of polar monomer units, v. 0 to 10 parts by weight of sitane_^funetiona! monomer units, wherein the sum of the monomer units is 100 parts by weight; b) a diluent monomer component, and c) a photoinitiator. wherein the composition comprises no erosslinkmg agents.

2. The adhesive composition of embodiment 1 comprising less than 50 wt.¾ of the diluent monomer component and greater -than 50 wt.% of the solute oligomer.

3. The adhesive of any of the previous embodiments wherein the monomer units having pendent acryiate groups are prepared by reaction of said oligomer having pendent hydroxy! functional groups with an acryloyl compound having co-reactive functions groups. 4. The adhesive of embodiment 3 wherein the acry!oyi compound having co-reactive functional groups Is of the formula:

wherein R is hydrogen, a Ci to C4 alkyi group, or a phenyl group,; R^* is a. single bond or a (hetero)hydrocarbyl divalent linking group that joins an cthyienically unsaturated group to co-reactive functional group A, and A is a carboxyi, isocyanato, epoxy, anhydride, or oxazo!myl group.

5. The adhesive of any of the pre vious embodiments, wherein the alkanol of the (meth)acr late ester monomer units of the oligomer have an average carbon number of

C¾ o-C{4-

6. The adhesive of any of the pre vious embodiments, wherein the hydroxyl-functional monomer has the general formula:

vnerein

s is a hydrocarbyl group;

R* is -H or C1-C4 alkyl; and

X' is -NR⁴- or- -.

7. The curable composition of any of the previous embodiments wherein the diluent monomer component comprises at least one monomer selected fro acrylate ester monomer units, hydrox l-funetionai monomer units; monomer units having pendent acrylate groups, polar monomer units, and siiane-functional monomer units.

8. The curable composition of any of the previous embodiments wherein the diluent monomer component comprises: 80 to 100 parts by weight of (meth)acrylate ester monomers;

0 to 20 parts- by weight of hydroxy-functional monomers;

0 to 5 parts by weight of polar monomers;

0 to 2 parts by weight of silane functional monomers, wherein the sum of the monomer of the diluent monomer component is 100 parts by weight.

9. The adhesive of any of the previous embodiments wherein the (meth)acry!ic acid ester monomer component may comprise (meth)acry!ate esters of 2-alkyl alkanols wherein the molar carbon number average of said 2-alkyl alkanols is 12 to 32.

10. The adhesive of any of the previous embodiments wherein the oligomer is of the formula:

-[M^fcsie!]- represents interpoIymer¼ed (meih)acrylate ester monomer units;

-|M^0H j- represents interpolymerized (meth)aeryloy! monomer units having a pendent hydroxy group,,

- M^Fo!ar]- represents inteFpoIymerized polar monomer units; and

[M^AcryS j represents interpolymerized (meth)acryloyl monomer units having a pendent poiynnerizable (meth)acry!oyi group;

[M^{s,i f}] represent optional silane-ftmctional monomer

subscripts -a, b*, e, d and represent the- parts by weight of each monomer unit. i 1. The curable composition of any of the previous embodiments further comprising an additive selected from heat stabilizers, antioxidants, antistatic agents, thickeners, fillers, pigments, dyes, colorants, thixotropic agents, processing aides, nanopariieles, fibers and any combination thereof.

12. The curable compositio of embodiment 1 1 wherein an additive is in amounts of 0,01 to 10 wt. % relative to the mass of curable composition. 13. The curable composition of any of the previous embodiments further comprising metal oxide particles having an average particle size of 1 ran to about 100 nra in amounts of 1 to 10 wt%_> relative to the total weight of the curable composiiion.

14. The curable composiiion of any of the previous embodiments wherein the hydroxyi-functienal monomer is used in amounts such that the curable composition (oligomer - diluent) has a hydroxy! content greater than 6.5 xlO^mol Οϊί/g.

15. The curable composition of any of the previous embodiments wherein the oligomer is prepared by an adiabatic polymerization process,

16. An optically clear laminate comprising:

a first substrate having at least one major surface;

a second substrate having at least one major surface; and

the curable composition of any of the previous embodiments 1 to 15 situated between and in contaci with at least one major surface of the .first substrate and at least one major surface of ^'the second substrate.

17. An optically clear laminate according to embodiment 16, wherein the first substrate, the second substrate, or both the first substrate and the second substrate are selected from a display panel, a touch panel, an optical film, a cover lens, or window.

18. An optically clear laminate according to embodiment 17, wherein the cover lens comprises at least one of glass, polymethylmethacrylate, or polycarbonate.

19. An optically clear laminate according to embodiment 17, wherein the display panel is selected from a liquid crystal display, a plasma display, an OLED display, an

eiectrowetting display, and a cathode ray rube display. 20. An optically clear laminate according to embodiment 17, wherei the optical film is selected from a reflector, a polarizer, a mirror, an anti-glare or anti-reflective film, an anti-splinter film, a difi ser, or electromagnetic interference filter.

21. A laminate according to any of the previous embodiments 16 to 20, wherein the curable composition has a thickness of greater than about 100 μηι.

22. A laminate according to embodiment 16, wherein at least one of the substrates is polycarbonate or polymethylmethacrylate.

23. An optically clear laminate comprising:

a first substrate having at least one major surface;

a second substrate havin at leas one major surface; and

an optically clear adhesive composition of any of the previous embodiments I to 15. situated beiween and in contact with at least one major surface of the first substrate and at least one major surface of the second substrate, wherein the adhesive has a moisture- vapor transmission rate of at least 400 g m7day.

24. A method of preparing an. adhesive comprising the steps of:

(i) providing an essentially curable composition of any of the previous embodiments 1 to 15.

(ii) partially polymerizing said composition to provide a partiall polymerized mixture exhibiting a Brookfield viscosity of beiween 1,000 and 500,000 Pas at 20°C and a degree of conversion of monomers to polymer of between 85-99 wt. %, with respect to the mass of the monomers pri or to polymerization,

(iii) converting a portion of the hydroxy! functional monomer units of said oligomer to pendent polymerizable (meih)acrylate groups,

(iv) adding one or more pbotolrsitiators and solvent diluent monomers to the partially polymerized mixture to provide a radiation-curable composition,

(iv) subsequently coating the radiation-curable composition on a substrate, and (v) further polymerizing the radiation-curable composition by subjecting it to actinic irradiation to provide said adhesive,

25. The method of embodimeat 24 wherein the radiation curable composition is coated by knife-coating, gravure coating, curtain coating, air knife coating spray coating, die coating, draw bar coating or curtain coating or roll-coating.

26. The method of embodiment 24 wherein the radiation curable composition is coated by applying dots and/or lines via a needle, needle die or slot die to the substrate.

27. The method of embodiment 24 further comprising a tackifier.

28. The method of embodiment 24 further comprising a pi astic izer.

Claims

What is claimed Is:

1. A curable composition comprising: a) a solute (meth)acryo!yl oligomer having a M_w of 5 to 30k and a T_g of < 20°C comprising i greater than 50 parts by weight of (meth)aerylate ester monomer units, si. ! 0 to 49 parts by weight of hydroxy i-funeti on al monomer units, Hi. i to 10 parts by weight of monomer nnits having pendent acry!ate groups, ry. 0 to 20 parts by weight of polar monomer -units, v. 0 to 10 parts by weight of siiane-fuoctionaJ monomer units, wherein the sum of the monomer units is 100 parts by weight; b) a diluent monomer component, and c) a pho oinitiatdr, wherein the composition comprises no erossliuki tg agents.

2. The adhesive composition of claim 1 comprising less than 50 wt.% of the diluent

monomer^' .component and greater than 50 wt.% of the ^'solute oligomer.

3. The adhesive of clai I wherein^' th monomer units having pendent aeryiate groups are prepared by reaction of said oligomer having pendent hydroxy! functional groups with -an acry!oy! compound having co-reactive functions groups.

4. The adhesive of claim 3 wherein the acryloyl compound having co-reactive functional groups is of the formula:

wherein R^J is hydrogen, a C_t to C₄ alkyl group, or a phenyl group,; R² is a single bond or a (hetero)hydrocarbyl divalent Unking -group that joins an ethyiemcai!y unsaturated group to co-reactive functional group A, and A is a carboxy!, isocyanato, epoxy, anhydride, or oxazoliny! group.

5. The adhesive of claim I , wherein the a!kano! of the (meth)acrylate ester monomer units of the oligomer have an average carbon nnmber of C^-C .

6. The adhesive of claim I , wherein the hydroxy! functional monomer has the genera! ibrmuis:

R⁵ is a hydrocarbyl group;

R⁴ is -H or C]-C₄ alky I; and

X^s is -NR⁴- or -0-.

7. The curable composition of claim 1 wherein the diluent monomer component comprises at least one monomer selected from aeryi&te ester monomer units, hydroxyf-iunctional monomer units; monomer units- having- pendent acry!ate groups, polar monomer units, and stkne-fknctiohal monomer units,

8. The curable composition of claim 1 wherein the diluent- monomer component comprises;

80 to 100 parts by weight of (meth)acrykte ester monomers;

0 to 20 parts by weight. of hydroxy-functiohal monomers;

0 to 5 parts by weight of polar monomers;.

0 to 2 ^'parts by weight of si lane ftinctional monomers, wherein the sum of the monomer of the diluent monomer component is 100 parts by weight.

9. The adhesive of claim I wherein the (meth)aeryiie acid ester monomer component may comprise (meth)acryiaie esters of 2-alky? a!kano!s wherein the molar carbon number average of said 2-afkyi alkanols is 12 to 32.

10. The adhesive of claim 1 wherei the oligomer is of the formula:

ΗΜ^¾!¾ Μ^ί;%^Μ^¾ί%-[Μ⁵*%- [Μ^Α<¾~, where

- M^i¾«^s]~

(meth)acrylate ester monomer units;

«[M°^rf]« represents interpolvmerized (meth)acryloy! monomer units having a pendent hydroxy group,

~fM^pQ¾rJ~ represents inierpofymerized polar monomer units; and

[M^Aw5*f represents isterpoiymerized (metis )acryioyl monomer units having a pendent

poiymerizab!e (fneih)acryloyf group;

[M^s,iyi] represent optional silane-ftmctional monomer

subscripts a, b*, c, d and represent the parts by weight of each monomer uni

11. he curable composition of claim I further comprising an additive selected from heat stabilizers, antioxidants, antistatic agents, thickeners, fillers, pigments, dyes, colorants, thixotropic agents, processing aides, nanoparticks, fibers and any combination thereof.

12. The curable composition of claim 1 1 wherein an additive is in amounts of 0.01 to 10 wt. % relative to the mass of curable composition.

13. The ..curable composition of claim I further comprising metal oxide particles having an average particle size of 1 nm to about 100 am in amounts of 1 to 10 wi.%, relative to the total weight of the curable composition.

14. The curable composition of claim: I wherein the hydfoxyl-funetional monomer is used in ■amounts such thai the curable composition (oligomer + diluent) has a hydroxy! content greater than 6.5 x! O^"4 mol G.H g.

15. The curable composition of claim i wherein the oligomer is prepared by an adiabatic polymerization process.

16, An optically clear laminate comprising:

a first substrate having at least one major surface;

a second substrate having at least one major surface; and

the curable composition of claim 1 si tuated between and in contact with at least one major surface of the first substrate, and at least one maj or surface of the second substrate.

17. An. optically clear laminate according to claim 16, wherein the first substrate, the second substrate, or both the first substrate and the second substrate are selected from a display pane!, a touch panel, an optical film, a cover lens, or window.

1 S, An optically clear laminate according to claim 17, wherein the cover lens comprises at least One of glass, polymethylmethacrylate, or polycarbonate.

19, An optically clear laminate according to claim 17, wherein the display panel is selected from a liquid crystal display, a plasma display, an OLED display, an elecirowetting display, and a cathode ray tube display.

20, An optically clear laminate according to claim 17, wherein the optical film is selected from a reflector, a polarizer, mirror, an anti-glare or anti-reflective film, an anti-splinter film, a diff ser, or electromagnetic interference filter.

21 , A laminate according to claim 16, wherein the curable composition has a thickness of greater than about 100 μ?η.

22. A laminate according to claim 16, wherein at least one of th substrates is polycarbonate or pojy( ethy l)methaery 1 ate ,

23. An optically clear laminate comprising:

a first substrate having at least one major surface;

a second substrate having at least one major surface; and

an optically clear adhesive composition of claim 1 situated between and in contact with at least one major surface of the first substrate and at least one major surface of the second substrate, wherein the adhesive has a moisture-vapor transmission rate of at least 400 g/m'/day.

24. A method of preparing an adhesive comprising the steps of:

(i) providing an essential ly curable composition of claim 1 ,

(ii) partially polymerizing said composition to provide a partially polymerized mixture exhibiting a Brookfteld viscosity of between 1,000 and 500,000 mPas at 20^aC and a degree of conversion of monomers lo polymer of between 85-99 wt. %, with respect to the mass of the monomers prior to polymerization,

(Hi) converting a. portion of the hydroxy! functional monomer units of said oligomer to pendent poIymeri2ahfe (m«th)acry1ate groups,

(iv) adding one or more photosniiiators and solvent diluent monomers to the partially polymerized mixture to provide a radiation-curable composition,

(iv) subsequently coating the radiation-curable composition on a substrate, and

(v) further polymerizing the radiation-curable composition by subjecting it to actinic irradiation to provide said adhesive.

25. The method of claim 24 wherein the radiation curable composition is coated by knife- coating, gravure coating, curtain coating, air knife coating spray coating, die coating, draw bar coating or curtain coating or roll-coating.

26. The method of claim 2.4 -wherein the radiation curable composition is coated by applying dots and/or lines via a needle, needle die or slot die to the substrate,

27. The method of claim 24 further comprising a tackifier.

28. The method of claim 24 further comprising a plasticizer.